1. Field of the Invention
The present invention relates to the prevention of static buildup on polymeric materials by the addition of antistatic layers to those materials. In particular, the invention relates to antistatic coatings in association with imageable materials.
2. Background of the Art
Many different polymeric materials have been long recognized as suffering from electrostatic charge buildup during use. The problems associated with such static charging may be as modest as sparks from moving about on polymeric carpeting and popping sounds on phonograph records or as serious as memory erasure on computer disks and false artifacts in photographic film.
One usual method of reducing static buildup is the addition of a conductive layer or low surface resistivity layer to the polymeric article. It is common in the protection of shaped polymeric articles, including carpets, to treat the polymer with reactive or absorbable salts (e.g., U.S. Pat. 3,309,223 and 4,313,978). It is also known to form layers of inorganic metal oxides, either in film or particulate form to decrease the surface resistivity (e.g., U.S. Pat. 4,203,769 and 4,394,441). These antistatic coatings are known to be particularly desirable and useful as subbing layers in photographic articles (e.g., U.S. Pat. 3,874,879).
Chitosan is an organic material derived from the shells of arthropods such as shrimp, crab, and lobster. Chemically, it is a d-glucosamine. Chitosan and its derivatives have been known to be used in diffusion transfer films (e.g., U.S. Pat. 4,386,151 and 4,383,022), cosmetic base (e.g., EPO 0 198 246), in paper products as an absorbent (e.g., JP 62-064803), and as part of a particulate antistatic coating on the back side of photographic base, especially photographic paper (JP 62-319842). The chitosan in that Japanese Patent Publication may be mixed with colloidal silica or alumina and may contain other additives such as antistatic modifiers. The solution is preferably coated at a pH above 5.0 to prevent effects on the photographic emulsion. The coatings are not transparent and the resistivity of compositions within and outside the invention are similar, suggesting little antistatic effect from the chitosan.